The purpose of this study is to test a sleep-medicine intervention to reduce the severity of symptoms related to Fibromyalgia (FM). Rationale: Research indicates that sleep disturbances might be maintaining or intensifying some of the symptoms of FM. Most patients with FM characterize their sleep as light, easily disturbed, and unrefreshing. Many patients with FM report insomnia. However, in addition to difficulty initiating and maintaining sleep, polysomnography (i.e., overnight sleep studies) document frequent nighttime arousals. Some of these arousals appear to be secondary to sleep disordered breathing (SDB). It would not be surprising if FM were comorbid with SDB considering that the symptoms of SDB are similar to symptoms of FM (e.g., fatigue, increased pain, etc.). Since treatment of SDB with continuous positive airway pressure (CPAP) can improve the above symptoms, treatment of SDB in FM patients might improve FM symptomatology as well. To date, only two studies have attempted this type of intervention. Unfortunately, neither used placebo controlled groups, which might mean that their significant results were simply a placebo effect, and none have combined this type of intervention with simple behavioral insomnia interventions. The primary aim of this pilot study is to complete the first adequately powered placebo controlled test of the relative efficacy of CPAP to treat SDB in patients with FM, while controlling for the effects of an insomnia intervention. The secondary aim is to increase the understanding of the role of sleep disorders (SDB and insomnia) in the FM disease process. Study design: A randomized, double-blind study design will be used to test the effectiveness of the CPAP intervention. Female participants with physician confirmed FM (N=32) will undergo diagnostic tests for SDB (overnight polysomnographic study). Participants with SDB will be randomly assigned to one of two conditions: active CPAP (n=16) and a sham-CPAP control condition (n=16) and treated for four weeks. In addition, half of each group will also receive a brief insomnia intervention. A weekly repeated measures strategy will be used to capture changes in FM symptoms and sleep patterns as a function of treatment. It is predicted that CPAP will improve common FM symptoms (e.g., fatigue, morning sleepiness, frequent awakenings, pain, pain helplessness, negative affect, functional disability) in and above the effects of an insomnia intervention. The long-term objective of this study is to develop an empirically supported, effective treatment for FM, thus reducing the high health care costs incurred by FM patients and minimizing patient suffering.